A light-emitting diode (LED) is a solid state semiconductor device which comprises at least one p-n junction formed between the p-type and n-type semiconductor layers. When a forward voltage is applied to the p-n junction, the electrons from the n-type semiconductor layer and the holes from the p-type semiconductor layer are combined to emit the light. The region where the light is emitted is generally named a light-emitting region.
The main features of the LED comprise the small size, the high luminous efficiency, the long life, the fast response, the high reliability, and the good quality in color performance. An LED is widely used in electrical equipments, automobiles, commercial signs, and traffic signals. With the advent of the full-color LED, the LED gradually replaces the traditional lighting such as fluorescent and incandescent bulbs.
With the substrate of the LED being soldered or glued to a submount, the LED can be further connected to the submount to form a light-emitting device. In addition, the submount may comprise at least one circuit, which is electrically coupled to electrodes of the LED through a conductive structure such as a metal wire.